The present invention relates generally to the field of bolts seals and, more particularly, to a sleeved bolt and seal construction which avoids some modes of defeating the seal function without detection.
Door closures and locks are often provided with a bolt and seal mechanism to stop intruders from jimmying the lock. Such a closure may comprise a hasp on a cargo door of a truck, for example, or other application. When a such a closure is jimmied, the intruder frequently will try to find a way of opening the closure without leaving evidence of the intrusion. Such mechanisms typically include a body, larger in diameter than the bolt, which attaches to or is integrally formed with the bolt on the end of the bolt opposite the bolt head. The bolt attaches to the interior of the body with a snap ring to provide an enlarged region on either side of the closure hasp to lock the closure. Other bolt seals may include a grip mechanism to prevent retraction of the bolt from the device in the direction opposite its insertion, such as that shown and described in U.S. Pat. No. 4,681,356 directed to cables, but equally adaptable to bolts.
To open the closure, the bolt must be cut with bolt cutters. Consequently, the length of the bolt between the bolt head and the body of the seal means must be longer than the thickness of the hasp in order to provide room for the bolt cutters to access and sever the bolt. And, if there is enough room for bolt cutters to gain access, then there is enough room for a jimmying tool to defeat the mechanism inside the body and thereby open the seal without leaving any evidence of intrusion. The jimmying tool is inserted between the bolt and the hasp and further into the wedge mechanism holding the bolt so that the body slides easily off the bolt, leaving no evidence that the mechanism has been defeated.
Thus, there remains a need for a bolt seal which eliminates the space between the bolt head and the hasp or closure, to prevent tampering with the seal mechanism. Such a bolt seal should be simple and inexpensive to manufacture, yet defeat the previously described modes of opening the closure without leaving evidence that the closure has been opened.
The present invention addresses these and other needs in the art by providing a bolt seal and lock mechanism equipped with a bolt gripping mechanism that is not easily defeated. The bolt seal provides a slidable sleeve surrounding a solid bolt body having a bolt head affixed at one end. The sleeve is held in abutting contact with the bolt head at one end of the sleeve and a shoulder comprising an enlarged diameter portion of the solid bolt body at the other end of the sleeve. In this first preferred embodiment, the bolt and seal form a polygon in cross-section to prevent rotation. The bolt head can therefore be pressed snug against a seal housing, thereby eliminating a mode of jimmying the seal, while simultaneously providing a means for opening the seal with bolt cutters when the seal must be opened.
The bolt body and sleeve, which make up the bolt, penetrate the housing in one direction, but a jam lock mechanism prevents motion of the bolt in the other direction. The jam lock mechanism includes a roller which rides on a ramp liner and is biased with a spring. The materials of the ramp liner, roller, sleeve, and bolt body are selected of various hardnesses to prevent opening the lock seal under force, as with a crow bar.
In another preferred embodiment of the lock seal, the bolt penetrates a rotatable body within the housing, and the bolt is preferably circular in cross section. The rotatable body includes a pair of jam lock mechanisms to hold the bolt stationary relative to the rotatable body and the housing.
These and other features of the present invention will be apparent to those skilled in the art from a review of the following detailed description along with the accompanying drawings.